Did they know you have MS before they gave you a perm? I've never heard of MS meds causing a perm not to take....but I've never researched it, either, so it's entirely possible. Seems like if they knew you took those types of meds they would have said something to you before giving you the perm.
At least they were fair about it and refunded your money. It's been years since I had a perm. I think I was in my 20's and I got a spiral perm. Wow! Talk about curly!